Binary Permission System Snippet

permissions.py

from django.db import models


class Permission:
    # Random permissions added here
    # Follow binary pattern 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, ...
    VIEW = 1
    EDIT = 2
    EXECUTE = 4
    MANAGE_OTHERS = 8
    STAFF = 16
    ROOT = 32


class Role(models.Model):
    """django model for permission"""

    name = models.CharField()
    permissions = models.IntegerField(default=0)

    def add_permission(self, perm):
        if not self.has_permission(perm):
            self.permissions += perm

    def remove_permission(self, perm):
        if self.has_permission(perm):
            self.permissions -= perm

    def reset_permissions(self):
        self.permissions = 0

    def has_permission(self, perm):
        # This does a bitwise AND
        return self.permissions & perm == perm

    def __str__(self):
        return f"Role {self.name}"


class User(AbstractUser):
    ...  # What already existed before this PR
    role = models.OneToOneField(Role)


# Inserting roles with permissions
def insert_roles():
    roles = {
        "User": [Permission.VIEW],
        "Manager": [Permission.VIEW, Permission.EDIT, Permission.EXECUTE],
        "Root": Permission().get_all_permissions(),
    }
    for r, permissions in roles.items():
        role, created = Role.objects.get_or_create(name=r)
        role.reset_permissions()
        for perm in permissions:
            role.add_permission(perm)
        role.save()


# Example of checking the binary permission management approach
r = Role(name="FooBar")
r.add_permission(Permission.EXECUTE)  # Add 4
r.add_permission(Permission.MANAGE_OTHERS)  # Add 8
r.has_permission(
    Permission.EXECUTE
)  # 12 & 4 == 4 # true, we have permissions 8 and 4 to make up 12
r.has_permission(
    Permission.MANAGE_OTHERS
)  # 12 & 8 == 8 # true, we have permissions 8 and 4 to make up 12
r.has_permission(Permission.VIEW)  # 12 & 1 == 1 # false, we do not have permission 1

me = User.objects.first()
me.role = r
me.save()

me.role.has_permission(Permission.VIEW)

This is intended as a conceptual example, applied to a Django codebase.

Feel free to adapt it to suit your own needs.